Drug interactions
Fosphenytoin + Tofacitinib
Severity: Moderate
Fosphenytoin and Tofacitinib: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Fosphenytoin is converted to phenytoin, a potent CYP3A4 inducer that can lower tofacitinib exposure. This may lead to loss of efficacy.
What this interaction means in plain words
Fosphenytoin and Tofacitinib can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Fosphenytoin belongs to Central Nervous System; Tofacitinib belongs to Musculoskeletal.
Why it happens
Phenytoin induces CYP3A4, increasing tofacitinib clearance.
What to do
Monitor for reduced clinical response to tofacitinib; consider an alternative therapy if response is lost.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Tofacitinib
- Baricitinib + Tofacitinib Contraindicated
- Cladribine + Tofacitinib Contraindicated
- Tofacitinib + Upadacitinib Contraindicated
- Abatacept + Tofacitinib Major
- Anti-thymocyte + Tofacitinib Major
- Antithymocyte globulin equine + Tofacitinib Major
Other interactions of Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Fosphenytoin with Tofacitinib?
MediHelp rates the interaction as moderate. Fosphenytoin and Tofacitinib can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Fosphenytoin is converted to phenytoin, a potent CYP3A4 inducer that can lower tofacitinib exposure. This may lead to loss of efficacy.
How serious is the interaction between Fosphenytoin and Tofacitinib?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for reduced clinical response to tofacitinib; consider an alternative therapy if response is lost.
What other medicines interact with Tofacitinib?
MediHelp also lists interactions of Tofacitinib with, for example, Baricitinib, Cladribine, Upadacitinib. The full list is on the Tofacitinib page.
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